An arrangement of Diploneis sp. (called Navicula on the slide) from Whitehaven (presumably the one on the north west coast of England). Prepared by William Allott Firth. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. 11mm tube the the camera removed to increase the field of view. Monochrome converted Nikon d850 camera. 48 images stacked in Zerene (Pmax).
As mentioned above, I think these are examples of what would now be called Diploneis diatoms. Maybe D. smithii, although that is a very tentative ID.